1. Field of the Invention
The present invention relates to a method for recording optical information which is suitably applied to an optical information read/write device such as an optical disk device, especially a read/write device which records optical marks with the use of the laser beam heat generated by irradiating the laser beam on the recording medium.
2. Description of the Related Art
An optical information read/write device records optical information data in such a way that a laser beam is irradiated on a recording medium so that the optical energy is absorbed by the recording medium film and that the optical energy involves the thermal function which forms holes in the film, changes the crystalline structure of the film or the magnetized direction of the film, or deforms the recording film so as to write optical marks on the recording medium. Such a method for recording the optical marks has been developed these days and applied to an optical disk device or a magneto-optical disk device. Such an optical device has advantages that the recording density is very high and the memory capacity is very large. Therefore, the device has been widely used as an external memory device.
The memory capacity of an optical disk device of today is 300 to 500 MB (megabyte) in one side of the disk of 130 mm diameter. However, it is required to further enlarge the memory capacity to the extent more than 1000 MB for the same size disk.
For that purpose, it becomes very important to heighten the recording linear density and the track density. However, for this purpose, if simply the interval of the recording position is shortened or the track pitch is narrowed, the signal interference between the adjacent marks becomes enlarged. Therefore, an only effective way for heightening the recording linear density or the track density has been to reduce the spot diameter of the optical beam for reading and writing the information data.
However, such a method of reducing the optical spot diameter is limited from the stand point of design of the optical system construction.